Rick,
Sorry, I've been out of town without a PC.
It will take time for Bernie to recover. He just went through major surgery. You need to be VERY patient. Do as you vet says. Keep him quiet and calm.
Our Murphy was far worse when he went in for surgery. He took a year just to stand on his own. Your Bernie is ahead of the game. Its a long road to recovery... and yes, you are expecting to much, too soon.